A) red light
B) yellow light
C) green light
D) blue light
Correct Answer: A
Solution :
From lens makers formula \[\frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] \[f\propto \frac{1}{(\mu -1)}\] \[f\propto \frac{1}{\mu }\] \[\Rightarrow \] \[\mu \propto \frac{1}{\lambda }\] So, \[f\propto \lambda \] But wavelength of red light is more as compared to other given light. Hence, focal length of convex lans is maximum for red light.
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